Meta-surfaces and antennas´ radiation characteristics enhancement: planar microstrip and microstrip-based quasi-aperture antennas

Meta-surfaces as artificial magnetic conductors or high impedance surfaces to control the electromagnetic fields excited by a microstrip patch resonator are investigated for planar and non-planar structures. In the planar structure, two types of meta-surfaces are used as electromagnetic transducers to transform the captured non-radiating waves to radiated space waves, leading to about 4 dBi gain enhancement. Alternatively, by applying these surfaces as E-plane fences in two sides of a patch, a compact microstrip-based quasi-aperture antenna is proposed. The proposed antenna not only improves the gain up to 8 dBi, but also provides almost a symmetric radiation pattern by controlling the phase distribution of electric fields in the antenna aperture. Using near electric-field pattern inspection and characterising the meta-surfaces, the radiation mechanism of the proposed antennas are delineated. Two antenna prototypes are fabricated and tested and, confirming the simulated ones, the corresponding measured results are presented.